#include <iostream>
using namespace std;
const int N = 110;
int n;
int dp[N][N];
int main()
{
	int x;
	cin >> n;
	for (int i = 1; i <= n; i++)
	{
		for (int j = 1; j <= n; j++)
		{
			cin >> x;
			dp[i][j] = dp[i - 1][j] + dp[i][j - 1] - dp[i - 1][j - 1] + x;
		}
	}
	int ret = -127 * N;
	for (int x1 = 1; x1 <= n; x1++)
	{
		for (int y1 = 1; y1 <= n; y1++)
		{
			for (int x2 = x1; x2 <= n; x2++)
			{
				for (int y2 = y1; y2 <= n; y2++)
				{
					ret = max(ret, dp[x2][y2] - dp[x1 - 1][y2] - dp[x2][y1 -
						1] + dp[x1 - 1][y1 - 1]);
				}
			}
		}
	}
	 cout << ret << endl;
	return 0;
}